Apparatus and method for alternating current physical signals measurement and data acquisition

ABSTRACT

An apparatus for AC physical signals measurement and data acquisition and the method for the same are provided. The apparatus for AC physical signals measurement and data acquisition comprises an analog sampling channel for inputting an AC signal and outputting an analog sampling value; a sampling switch for performing re-sampling to obtain data frequency as required by the receiving side; a register for storing a re-sampling value from the sampling switch; a bus for outputting the re-sampling value in the register to the receiving side; a timing controller for controlling the analog sampling channel and the re-sampling frequency of the sampling switch; and a digital low-pass filter, which has an input connected with the analog sampling value outputted by the analog sampling channel and an output connected with the sampling switch, filters out high frequency components from the sampling value, and has a cut-off frequency that should be lower than 0.5 times the re-sampling frequency of the sampling switch. The apparatus and method for AC physical signals measurement and data acquisition improve accuracy of remote measurement for electric power physical quantities. Not only waveform values are outputted by re-sampling, effective values, steady state values and their fundamental/harmonic wave effective values and steady state values are also outputted. Thus, various requirements by the receiving side on remote measurement data are satisfied.

TECHNICAL FIELD

The invention relates to techniques for power system automation, andparticularly, to an apparatus and method for alternating current (AC)physical signals measurement and data acquisition.

BACKGROUND

In power dispatching automation, measurement and data acquisition forelectric power physical quantities was performed by a Remote TerminalUnit (RTU) in the early days, and has been performed by substationintegrated automation in recent years. It is performed by a measuringunit in a digital substation; by an electric energy meter or adistribution transformer terminal in power utilization automation (suchas power utilization information system, intelligent power utilization);by a power distribution switch terminal in power distributionautomation; or by a measuring and transducing unit in a generatorexcitation controller. In all the measuring units or terminals mentionedabove, the measurement and data acquisition (simply referred to as“remote measurement” hereinafter) process is such that an AC current iand an AC voltage u are inputted and sampled at a predetermined samplinginterval Δ (analog-digital conversion) to obtain a sampling value i_(k)of the current and a sampling value u_(k) of the voltage; other physicalparameters, such as AC current effective value I_(k), AC voltageeffective value U_(k), active power P_(k), reactive power Q_(k) (k=1, 2,. . . ) and the like, are then calculated from i_(k) and u_(k), andP_(k) and Q_(k) are accumulated to derive active electric energy W_(k)and reactive electric energy V_(k); then, re-sampling is performed at aninterval of M (also known as freezing of data by a timing designated bythe receiving side) to output re-sampling values I_(j), U_(j), P_(j) andQ_(j) of the electric power physical quantities to the receiving side.The receiving side can receive them locally or remotely. Local receptioncan occur within the same apparatus, or within a different apparatusdeployed nearby. Remote reception occurs from a long distance. Thereceived remote measurement data is applied on the receiving side.

In the above remote measurement process, the sampling interval Δgenerally can satisfy the Shannon sampling theorem, that is, thesampling frequency f_(Δ)=1/Δ>2×f_(c) (where f_(c) is the cut-offfrequency of the sampled signal). Therefore, the calculated effectvalues of the physical quantities, such as I_(k), U_(k), P_(k) andQ_(k), do not have the aliasing problem. However, after the re-sampling,since the re-sampling frequency f_(W)<f_(c) does not satisfy the Shannonsampling theorem, there will be an aliasing of high frequency componentsinto low frequency components and as a result, an aliasing error willarise.

Currently, new energy power generation, direct-current (DC) transmissionand non-linear load have been increasingly prevalent, and harmonic wavecontent has been greater and greater in power systems. As a result, thealiasing error as mentioned above has become larger and larger. Sincecalculation of reactive power requires an assumption that the currentand voltage are sinusoidal signals, the error of reactive power andreactive electric energy is even bigger, to an extent that cannot beignored.

For the receiving side, the effect values of the fundamental wavecomponents, i.e., I_(j) ¹, U_(j) ¹, P_(j) ¹ and Q_(j) ¹, are morevaluable than the effect values I_(j), U_(j), P_(j) and Q_(j). Forthree-phase AC, fundamental wave positive sequence components, i.e.,I_((1)j) ¹, U_((1)j) ¹, P_((1)j) ¹ and Q_((1)j) ¹, are more valuablethan three-phase effect values I_(j), U_(j), P_(j) and Q_(j). However,no measuring units or apparatuses of the prior art have outputtedfundamental wave components and positive sequence components. As aresult, it is difficult to apply electric power physical quantities atthe receiving side.

Re-sampling in power applications is divided into three categories: (1)re-sampling of i_(k) and u_(k) to output i_(j) and u_(j), which iscalled waveform re-sampling, with the re-sampling interval denoted byM_(W), and the output being waveform values; (2) quick re-sampling ofI_(k), U_(k), P_(k) and Q_(k), which is called effective valuere-sampling, with the re-sampling interval denoted by M_(T), and theoutput being effect values; (3) slow re-sampling of I_(k), U_(k), P_(k)and Q_(k), which is called steady state re-sampling, with there-sampling interval denoted by M_(S), and the output being steady statevalues. Typically, M_(W)<M_(T)<M_(S).

Chinese Invention Patents ZL200910158375.x and ZL200910158370.7 (to HaoYuShan, entitled “CONTINUOUS PHYSICAL SIGNALS MEASUREMENT DEVICE ANDMETHOD”) provides steady state data remote measurement and full statedata remote measurement for general physical data. However, the outputfrequency does not conform to the above re-sampling frequency. Also, toomany contents are outputted. It is thus inconvenient to apply itdirectly to power automation systems.

SUMMARY

In view of the foregoing, an objective of the present invention is toprovide an electric power physical signal remote measurement apparatusand method for inputting an AC current i and/or an AC voltage u(referred to as AC) and outputting AC waveform values, effective valuesor steady state values and effective values or steady state values oftheir fundamental wave and sequence components, as required by thereceiving side.

An apparatus for AC physical signals remote measurement according to theinvention, comprising:

an analog sampling channel for performing analog sampling on an input ACsignal to output an analog sampling value;

a sampling switch for performing re-sampling to obtain remotemeasurement data frequency as required by the receiving side;

a register for storing the re-sampling value from the sampling switch;

a bus for outputting the re-sampling value in the register to thereceiving side;

a timing controller for controlling the analog sampling channel and there-sampling frequency of the sampling switch; and

a digital low-pass filter, which has an input connected with the analogsampling value outputted by the analog sampling channel and an outputconnected with the sampling switch, filters out high frequencycomponents from the sampling value, and has a cut-off frequency thatshould be lower than 0.5 times the re-sampling frequency of the samplingswitch.

If remote measurement of AC effective values is desired, then inaddition to the elements of the above solution, an effective valuecalculation device needs to be further provided between the analogsampling channel and the digital low-pass filter for calculating aneffect value for the sampling value from the analog sampling channel andoutputting it to the low-pass filter.

If remote measurement of AC harmonic wave effective values is desired,then in addition to the elements of the above solution for effectivevalue remote measurement, a harmonic wave decomposition device needs tobe further provided in parallel with the effective value calculationdevice between the analog sampling channel and the digital low-passfilter. The harmonic wave decomposition device includes afundamental/harmonic wave decomposition device for performingfundamental/harmonic wave decomposition on the sampling value from theanalog sampling channel to obtain a fundamental/harmonic wave vector;and an amplitude calculation device, a real part calculation device andan imaginary part calculation device, which receive thefundamental/harmonic wave vector from the fundamental/harmonic wavedecomposition device simultaneously to output a fundamental/harmonicwave amplitude, a fundamental/harmonic wave real part and afundamental/harmonic wave imaginary part, respectively, to the digitallow-pass filter.

Since during the process of harmonic wave decomposition, data amount ofremote measurement will increase remarkably, the remote measurementapparatus with harmonic wave decomposition needs to include:

a selection data register for storing selection data set by thereceiving side though the bus; and

a selection switch provided before the register, wherein for selectionbits controlled by the selection data register, when a selection bit is1, the data is selected and the re-sampling value enters into theregister to be stored; otherwise, the re-sampling value is not in theregister.

If only the data of the m^(th) harmonic wave is desired, a harmonic waveorder register may be provided for storing harmonic wave order data mset by the receiving side to control the fundamental/harmonic wavedecomposition device to output an m^(th) harmonic wave vector.

If measurement of three-phrase AC signals is performed, then in additionto the elements of the above apparatus for AC physical signals remotemeasurement, a sequence decomposition device is further provided, whichperforms sequence decomposition on the three single-phasefundamental/harmonic wave values outputted by the fundamental/harmonicwave decomposition device to obtain three-phrase AC positive sequencecomponents, negative sequence components and zero sequence components,each of which goes through the amplitude calculation device, the realpart calculation device and the imaginary part calculation devicesimultaneously to output positive sequence, negative sequence, and zerosequence effective values, real parts and imaginary parts, which arefiltered by the digital low-pass filter to remove high frequencycomponents.

If remote measurement is performed with respect to the AC steady state,then in the above solution, the digital low-pass filter includes:

an averaging device which is connected with the effective valuecalculation device for obtaining an average value of the AC effectivevalue outputted by the effective value calculation device, the real partand the imaginary part; and

a judging device which is connected with the effective value calculationdevice, and provides a flag F to the averaging device in accordance withthe effective value outputted by the effective value calculation device,wherein when the effective value is in a steady state process, F=0;otherwise, when the effective value is in a transient state process,F=1; and when F changes from 1 to 0, the average value is reset to zero,and when F=1, the average value is a value that cannot be reached,which, upon arrival at the receiving side, is removed as bad data.

The invention also provides an AC remote measurement apparatus suitablefor use in metering and measuring devices such as a single-phaseelectric energy meter or the like, the apparatus comprising:

an analog sampling channel for inputting an AC current i and an ACvoltage u and outputting a current sampling value i_(k) and a voltagesampling value u_(k);

a multiplication accumulator for inputting the current sampling valuei_(k) and the voltage sampling value u_(k) and outputting activeelectric energy W_(k);

a harmonic wave decomposition device for performing fundamental andharmonic wave decomposition on the current sampling value i_(k) and thevoltage sampling value u_(k) to obtain fundamental and m^(th) harmonicwave vectors;

an amplitude calculation device for inputting the fundamental and m^(th)harmonic wave vectors from the harmonic wave decomposition device andoutputting fundamental and m^(th) harmonic wave amplitudes;

a power calculation device for inputting the voltage and currentfundamental and m^(th) harmonic wave vectors from the harmonic wavedecomposition device to obtain fundamental and m^(th) harmonic waveactive power and reactive power;

an accumulator for inputting and accumulating the fundamental wavereactive power from the power calculation device and outputting reactiveelectric energy;

an averaging device for inputting the fundamental and m^(th) harmonicwave amplitudes from the amplitude calculation device and thefundamental and m^(th) harmonic wave active power and reactive powerfrom the power calculation device and outputting their average values ina steady state;

a sampling switch for inputting the average values from the averagingdevice and the active electric energy and the reactive electric energyfrom the accumulators, performing re-sampling, and outputting theirre-sampling values;

a register for storing the re-sampling values from the sampling switch;

a bus for outputting the re-sampling values in the register to thereceiving side;

a judging device for sending a flag F to the averaging device inaccordance with the fundamental wave voltage amplitude, the fundamentalwave current amplitude or the fundamental wave power are in the steadystate or transient states, wherein when the flag F changes from 1 to 0,the averaging device is reset to zero, and when F=1, the output of theaveraging device is a value that cannot be reached, which is removed asbad data on the receiving side;

a timing control device for performing timing control on the analogsampling channel and the sampling switch;

a selection data register for storing selection data set by thereceiving side through the bus; and

a harmonic wave order register for storing harmonic wave order data mset by the receiving side to control the fundamental/harmonic wavedecomposition device to output fundamental and m^(th) harmonic wavevectors.

As to remote measurement of a three-phrase AC electric energy meter, itis cannot simply repeat the processes of the above AC remote measurementapparatus. A sequence decomposition device needs to be provided forinputting the three single-phase voltage and currentfundamental/harmonic wave vectors from the fundamental/harmonic wavedecomposition device to perform sequence decomposition and outputtingthree-phrase voltage and current positive, negative, and zero sequencevectors to the amplitude calculation device.

The invention also provides a method for AC physical signals remotemeasurement, comprising:

performing analog sampling on an input AC voltage u and/or an AC currenti at a sampling interval of Δ to obtain a voltage sampling value u_(k)and/or a current sampling value i_(k);

performing low-pass filtering on the voltage sampling value u_(k) and/orthe current sampling value i_(k) to remove high frequency components,wherein a cut-off frequency fc of the low-pass filtering satisfiesfc≦0.5×f_(W) (f_(W) being the re-sampling frequency);

performing re-sampling at an interval of M_(W) designated by thereceiving side to obtain a voltage re-sampling value u_(j) and/or acurrent re-sampling value i_(j);

storing the voltage re-sampling value u_(j) and/or the currentre-sampling value i_(j); and

outputting the stored data to the receiving side.

In the above solution, the function of the low-pass filtering is tofilter out high frequency components, such that an aliasing error willnot arise in the re-sampling. The transfer function of the low-passfiltering is chosen as:

${G(z)} = \frac{1}{a_{0} + {a_{1} \cdot z^{- 1}} + \ldots + {a_{n} \cdot z^{- n}}}$where n=2, 4, 6, 8 and is the order of the filter; and G(z) is usuallyan n^(th) Butterworth filter or an n^(th) Chebyshev filter.

If remote measurement of effective values is desired, then in additionto the elements of the above solution, effective values of the analogsampling values need to be further calculated between the analogsampling and the low-pass filtering.

If remote measurement of harmonic waves is desired, then in addition tothe elements of the above solution for effective value remotemeasurement, harmonic wave decomposition needs to be further performedin parallel with the effective value calculating step between the analogsampling and the low-pass filtering.

Since during the process of calculating effective values of harmonicwaves, data amount of remote measurement will increase remarkably, theremote measurement method with harmonic wave decomposition needs toinclude:

storing selection data inputted by the receiving side; and

providing a selection switch after the sampling switch, wherein forselection bits controlled by the selection data, when a selection bit is1, the data is selected and the re-sampling value enters into theregister to be stored; otherwise, the re-sampling value is not stored.

If only the data of the m^(th) harmonic wave is desired, then harmonicwave order m set by the receiving side may be stored to control theharmonic wave decomposition to output an m^(th) harmonic wave vector.

Harmonic wave decomposition is performed on i_(k) and/or u_(k) inaccordance with the order m designated by the receiving side to obtainan m^(th) harmonic wave vector of current, İ_(k) ^(m), and/or an m^(th)harmonic wave vector of voltage, {dot over (U)}_(k) ^(m). Harmonic waveactive power component P_(k) ^(m) and harmonic wave reactive powercomponent Q_(k) ^(m) are derived from İ_(k) ^(m) and {dot over (U)}_(k)^(m). P_(k) ^(m)=Re(Ĩ_(k) ^(m)·{dot over (U)}_(k) ^(m)), and Q_(k)^(m)=Im(Ĩ_(k) ^(m)·{dot over (U)}_(k) ^(m)). Here, Ĩ_(k) ^(m) is theconjugate of İ_(k) ^(m), Re( ) denotes taking the real part, and Im( )denotes taking the imaginary part. m=1, 2, 3, . . . When m=1, it is thefundamental wave, which usually must be selected. In addition, one ormore values of m are designated by the receiving side provisionally, andone or more designated harmonic waves can be measured.

I_(k) ^(m) (which is the amplitude of İ_(k) ^(m)) and/or U_(k) ^(m)(which is the amplitude of {dot over (U)}_(k) ^(m)), P_(k) ^(m) andQ_(k) ^(m) also subject to the low-pass filtering and the re-sampling asdescribed above, to output harmonic wave effective values I_(j) ^(m)and/or U_(j) ^(m), P_(j) ^(m) and Q_(j) ^(m).

If measurement of three-phrase AC signals is performed, then in additionto the elements of said AC remote measurement method, a sequencedecomposition step needs to be further provided to perform sequencedecomposition on the three single-phase voltage and/or currentfundamental/harmonic wave vectors outputted by the fundamental/harmonicwave decomposition step to obtain three-phrase voltage and/or currentpositive, negative and zero sequence vectors, each of which is subjectto amplitude calculation, real part calculation and imaginary partcalculation simultaneously to output voltage and/or current positive,negative and zero sequence effective values, real parts and imaginaryparts, which are low-pass filtered to remove high frequency components.

The positive, negative and zero sequence is given by the followingwell-known equation:

$\begin{bmatrix}{\overset{.}{I}}_{{(1)}k}^{m} \\{\overset{.}{I}}_{{(2)}k}^{m} \\{\overset{.}{I}}_{{(0)}k}^{m}\end{bmatrix} = {\frac{1}{3} \cdot \begin{bmatrix}1 & {\mathbb{e}}^{j\frac{2}{3}\pi} & {\mathbb{e}}^{{- j}\frac{2}{3}\pi} \\1 & {\mathbb{e}}^{{- j}\frac{2}{3}\pi} & {\mathbb{e}}^{j\frac{2}{3}\pi} \\1 & 1 & 1\end{bmatrix} \cdot \begin{bmatrix}{\overset{.}{I}}_{ka}^{m} \\{\overset{.}{I}}_{kb}^{m} \\{\overset{.}{I}}_{kc}^{m}\end{bmatrix}}$where İ_(ka) ^(m), İ_(kb) ^(m), and İ_(kc) ^(m) are the k^(th)calculated values of the m^(th) harmonic wave vector of the A-phrase,B-phrase, and C-phase currents, respectively, and İ_((1)k) ^(m),İ_((2)k) ^(m) and İ_((0)k) ^(m) are positive, negative and zero sequencevectors of the m^(th) harmonic wave of the three-phrase currents,respectively. The positive, negative and zero sequence vectors of them^(th) harmonic wave of the three-phrase voltages can also be obtainedaccording to this equation.

If remote measurement is performed with respect to the steady state ofthe voltage and/or current, then the above method further comprises:

averaging the obtained effective values to obtain their average valuesŪ_(k) and/or Ī_(k), P _(k), and Q _(k); and

performing a steady/transient state determination for sending a flag Fto the average values in accordance with the outputted effective values,wherein when the effective values are in a steady state process, F=0;otherwise, when the effective values are in a transient state process,F=1; and when F changes from 1 to 0, the average values are reset tozero, and when F=1, the average values are values that cannot bereached, which are removed as bad data upon arrival at the receivingside.

In the above method, the averaging is also a kind of low-pass filtering.

The method for averaging is:

$\begin{matrix}{{\overset{\_}{x}}_{k} = {\frac{1}{k} \cdot {\sum\limits_{l = 1}^{k}\; x_{l}}}} \\{\left. {= {\frac{1}{k} \cdot \left\lbrack {{\left( {k - 1} \right) \cdot {\overset{\_}{x}}_{k - 1}} + x_{k}} \right)}} \right\rbrack.}\end{matrix}$

In the determination step, the determination is performed as follows. Avariance of the input data x_(k) (x_(k)=I_(k) or U_(k) or P_(k)) iscalculated:

${\hat{s}}_{k}^{2} = {{\frac{k - 2}{k - 1}{\hat{s}}_{k - 1}^{2}} + \left( {{\overset{\_}{x}}_{k} - {\overset{\_}{x}}_{k - 1}} \right)^{2} + {\frac{1}{k - 1}{\left( {{\overset{\_}{x}}_{k} - x_{k}} \right)^{2}.}}}$If |x_(k)−x _(k)|≦√{square root over (k)}·t_(α/2)(k−1)·ŝ_(k), it is inthe steady state. Here, x _(k) is the average value, t_(α/2) is astudent distribution, α is a risk level designated by the receivingside. The determination is applied to each of I_(k) or U_(k) or P_(k). Asteady state requires strict application, in which the F outputtedequals to 0 only if the F is 0 in all the three determinations.Generally, it is sufficient to input only P_(k) for determination.

The determination may also be constructed in accordance with filters. α,β and γ filtering is performed on an input data x_(k) (x_(k)=I_(k) orU_(k) or P_(k)), to obtain a location component S_(k), a velocitycomponentv_(k) and an acceleration component a_(k) of x_(k). If|a_(k)|≧a_(g), then it is in a transient state and F=1; otherwise, it isin a steady state and F=0. Here, a_(g) is a given value. If strictapplication is required, then there may be additional determinations. If|v_(k)|≧v_(g), then it is in a transient state and F=1; only if both|a_(k)|<a_(g) and |v_(k)|<v_(g) are satisfied, it is in a steady stateand F=0. Here, v_(g) is a given value. a_(g) and v_(g) are related tothe bandwidth, i.e. the time constant, of signal x_(k). Detailedinformation can be found in materials related to design of α, β and γfilters or design of Kalman filters.

The present invention also provides a method for AC remote measurementsuitable for use in a single-phase electric energy meter or the like,comprising:

performing analog sampling on an input AC current i and an AC voltage uto output a current sampling value i_(k) and a voltage sampling valueu_(k);

performing multiplication accumulation on the current sampling valuei_(k) and the voltage sampling value u_(k) to output active electricenergy W_(k);

performing low-pass filtering on the current sampling value i_(k) andthe voltage sampling value u_(k) to remove high frequency components,wherein a cut-off frequency fc of the low-pass filtering satisfiesfc≦0.5×f_(W) (f_(W) being the re-sampling frequency);

performing re-sampling on the low-pass-filtered sampling values toobtain re-sampling values;

performing fundamental/harmonic wave decomposition on the re-samplingvalues to obtain fundamental and m^(th) harmonic wave vectors;

calculating amplitudes of the fundamental and m^(th) harmonic wavevectors to output fundamental and m^(th) harmonic wave amplitudes;

calculating power of the fundamental and m^(th) harmonic wave vectors toobtain fundamental and m^(th) harmonic wave active power and reactivepower;

averaging the fundamental and m^(th) harmonic wave amplitudes, activepower and reactive power to output their average values in a steadystate;

accumulating the fundamental wave reactive power to output reactiveelectric energy;

re-sampling the average values, the active electric energy and thereactive electric energy to output their re-sampling values;

storing the re-sampling values;

outputting the stored re-sampling values to the receiving side through abus; and

a determining step for sending a flag F to the average values inaccordance with the fundamental wave voltage amplitude, the fundamentalwave current amplitude or the fundamental wave power in steady state orin transient states, wherein when the flag F changes from 1 to 0, theaverage values are reset to zero, and when F=1, the average values arevalues that cannot be reached, which are removed as bad data on thereceiving side.

For three-phrase AC, the present invention further provides an AC remotemeasurement method suitable for used in a three-phrase electric energymeter or the like, which, in addition to the elements of the abovemethod for AC physical signal remote measurement, further comprises afundamental/harmonic wave decomposition step, an amplitude calculationstep, a real part calculation step and an imaginary part calculationstep to output amplitudes, real parts and imaginary parts of thethree-phrase AC fundamental/harmonic wave positive, negative, and zerosequence components to the averaging step.

For AC, the analog sampling channel is used to obtain both voltage andcurrent sampling values. Current and voltage effective values and powerare calculated accurately. Not only waveform values are outputted byre-sampling, effective values, steady state values and their fundamentaland harmonic wave effective values and steady state values are alsooutputted. Low-pass filtering before the re-sampling avoids aliasingerrors. Determination of steady state ensures that transient state datawill not sneak into steady state data. Thus, various requirements by thereceiving side on remote measurement data are satisfied.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a single-phase AC voltage waveform remote measurementapparatus and method according to the invention.

FIG. 2 shows a single-phase AC voltage effective value remotemeasurement apparatus and method according to the invention.

FIG. 3 shows a single-phase AC voltage effect value remote measurementapparatus and method with harmonic wave decomposition according to theinvention.

FIG. 4 shows a variant of the apparatus of FIG. 3.

FIG. 5 shows another variant of the apparatus of FIG. 3.

FIG. 6 shows a three-phrase voltage remote measurement apparatus andmethod with harmonic wave decomposition according to the invention.

FIG. 7 shows a voltage steady state value remote measurement apparatusand method.

FIG. 8 shows a single-phase AC remote measurement apparatus and method.

FIG. 9 shows a three-phrase AC remote measurement apparatus and method.

DETAILED DESCRIPTION

Embodiments of the apparatus and method according to the invention willbe described below in connection with the accompanying drawings.

FIG. 1 shows a single-phase AC voltage waveform remote measurementapparatus and method.

In FIG. 1, the voltage waveform remote measurement apparatus includes ananalog sampling channel 1, a sampling switch 2, a register 3, a bus 4,and a timing controller 5. The apparatus further includes a digitallow-pass filter 6. An input AC voltage signal u goes through the analogsampling channel 1 to output a voltage sampling value u_(k), which isfiltered by the digital low-pass filter 6 to remove high frequencycomponents and then sent to the sampling switch 2. Re-sampling isperformed by the sampling switch 2, and then a voltage re-sampling valueu_(j) is outputted and stored in the register 3. Under the control ofthe bus 4, the register 3 outputs data to the receiving side through thebus 4. The analog sampling channel 1 and the sampling switch 2 arecontrolled by the timing controller 5. The function of the digitallow-pass filter 6 is to filter out high frequency components, and itscut-off frequency f_(c) should be lower than 0.5 times the re-samplingfrequency f_(W).

The apparatus of the embodiment of FIG. 1 is also applicable to currentwaveform remote measurement, as long as the voltage signals are replacedwith current signals. Similarly, the apparatus of FIG. 1 is alsoapplicable to waveform remote measurement for multi-phase voltage andmulti-phase current.

FIG. 2 shows a single-phase AC voltage effect value remote measurementapparatus and method.

In FIG. 2, the single-phase AC voltage effect value remote measurementapparatus includes an analog sampling channel 1, an effect valuecalculation device 7, a sampling switch 2, a register 3, a bus 4, and atiming controller 5. The apparatus further includes a digital low-passfilter 6. An input voltage signal u goes through the analog samplingchannel 1 to output a voltage sampling value u_(k), which goes throughthe effect value calculation device 7 to output a voltage effect valueU_(k). The voltage effect value U_(k) is filtered by the digitallow-pass filter 6 to remove high frequency components and then sent tothe sampling switch 2. Re-sampling is performed by the sampling switch2, and then a voltage re-sampling value U_(j) is outputted and stored inthe register 3. Under the control of the bus 4, the register 3 outputsdata to the receiving side through the bus 4. The analog samplingchannel 1 and the sampling switch 2 are controlled by the timingcontroller 5. The function of the low-pass filter 6 is to filter outhigh frequency components, and its cut-off frequency f_(c) should belower than 0.5 times the re-sampling frequency f_(T).

The apparatus and method of the embodiment of FIG. 2 are also applicableto single-phase current effect value remote measurement, as long as thevoltage signals are replaced with current signals. Similarly, theapparatus and method of FIG. 2 are also applicable to effect valueremote measurement for multi-phase voltage and multi-phase current.

FIG. 3 shows a single-phase AC voltage effect value remote measurementapparatus and method with a harmonic wave decomposition device.

In FIG. 3, a fundamental wave decomposition process is further includedin addition to the elements of FIG. 2. The voltage sampling value u_(k)outputted from the analog sampling channel 1 goes through a fundamentalwave decomposition device 81 to obtain a fundamental wave vector {dotover (U)}_(k) ¹·{dot over (U)}_(k) ¹ is inputted to each of an amplitudecalculation device 82, a real part calculation device 83 and animaginary part calculation device 84 simultaneously to output a voltagefundamental wave amplitude U_(k) ¹, a voltage fundamental wave real partUr_(k) ¹ and a voltage fundamental wave imaginary part Ui_(k) ¹,respectively. The U_(k) ¹, Ur_(k) ¹ and Ui_(k) ¹ are also filtered bythe digital low-pass filter 6 to remove high frequency components, andthen re-sampled by the sampling switch 2 to be outputted and stored inthe register 3.

FIG. 4 shows a variant of FIG. 3. In practical applications, the realpart and imaginary part of the fundamental wave are often used, whilethe effect value and the fundamental wave effect value may not be usedso often. Therefore, as shown in FIG. 4, a selection data register 31for registering selection data may be further included in addition tothe elements of FIG. 3. The selection data written in the selection dataregister 31 is controlled from the receiving side by the bus 4. Aselection switch 32 is provided after the sampling switch 2. For databits controlled by the selection data register 31, when a selection bitis 1, the data is selected and enters into the register 3; otherwise,the data is not in the register 3. Thus, whether the effect value, thefundamental wave effect value, and the real part and imaginary part ofthe fundamental wave are inputted into the register 3 is controlled bythe selection data written from the receiving side.

The apparatus and method of FIG. 3 may also be used for harmonic wavecomponents, as shown in FIG. 5.

FIG. 5 shows another variant of FIG. 3.

In addition to the elements of FIG. 3, a harmonic wave frequencyregister 33 is further included in FIG. 5 for registering data m. Datawritten to the harmonic wave frequency register 33 from the receivingside is controlled by the bus 4. The output of the harmonic wavefrequency register 33 is connected to the harmonic wave decompositiondevice 81 to control the harmonic wave decomposition device 81 to outputan m^(th) harmonic wave vector {dot over (U)}_(k) ^(m). Other elementsare the same as those of FIG. 3.

Three-phase voltage is applied to FIG. 4, as shown in FIG. 6. Here,[u_(k)] denotes a vector constituted by three-phrase voltage samplingvalues u_(ak), u_(bk), and u_(ck). The same applies to other signals. Inaddition to the elements of FIG. 4, a sequence decomposition device 9 isfurther included. The three single-phase voltage fundamental wave values[{dot over (U)}_(k) ¹] outputted by the fundamental wave decompositiondevice 81 of FIG. 4 are inputted to the sequence decomposition device 9to obtain a positive sequence component {dot over (U)}_((1)k) ¹. {dotover (U)}_((1)k) ¹ goes through each of the amplitude calculation device82, the real part calculation device 83 and the imaginary partcalculation device 84 simultaneously to obtain a positive sequenceeffect value, real part and imaginary part, which are filtered by thedigital low-pass filter 6 to remove high frequency components. Thenumber of bits of the selection data register 31 and that of the switch32 are increased accordingly. Other elements are the same as those ofFIG. 4.

If an application requires, processes for negative sequence and zerosequence may be added in addition to the elements of FIG. 6.

FIG. 7 shows a voltage steady state value remote measurement apparatusand method.

In FIG. 7, the voltage steady state value remote measurement apparatusaccording to the invention includes an analog sampling channel 1, aneffect value calculation device 7, a sampling switch 2, a register 3, abus 4, and a timing controller 5. The digital low-pass filter 6 furtherincludes an averaging unit A1 and a determination unit A2 provided afterthe effect value calculation device 7. After an analog voltage u isinputted, it goes through the analog sampling channel 1 and the effectvalue calculation device 7 to output a voltage effect value U_(k).U_(k), on one hand, goes through the averaging unit A1 to output avoltage average value Ū_(k), which is then re-sampled by the samplingswitch 2 to be registered into register 3. The register 3, under thecontrol of bus 4, outputs data through the bus 4 to the receiving side.On the other hand, U_(k) is inputted into the determination unit A2,which provides a flag F to the averaging unit A1. When U_(k) is in asteady state process, F=0; otherwise, when U_(k) is in a transient stateprocess, F=1. When F changes from 1 to 0, the average value Ū_(k) isreset to zero. When F=1, Ū_(k) is a value that cannot be reached. Uponarrival at the receiving side, values that cannot be reached by Ū_(k)are removed as bad data.

Similarly, in accordance with FIGS. 3-6 and 7, outputs of fundamentalwave, harmonic wave and positive sequence (negative sequence, zerosequence) steady state values can be obtained.

Active power P, reactive power Q, active electric energy W and reactiveelectric energy V can be derived from the sampling values of voltage andcurrent. Fundamental wave active power P¹, fundamental wave reactivepower Q¹, fundamental wave active electric energy W¹ and fundamentalwave reactive electric energy V¹ can be derived from the fundamentalwave voltage and the fundamental wave current. Fundamental wave positivesequence active power P¹ ₍₁₎, fundamental wave positive sequencereactive power Q¹ ₍₁₎, fundamental wave positive sequence activeelectric energy W¹ ₍₁₎ and fundamental wave positive sequence reactiveelectric energy V¹ ₍₁₎ can be derived from the fundamental wave positivesequence voltage and the fundamental wave positive sequence current.Thus, their effect value output and steady state value output can beobtained.

Combining the above apparatuses, FIG. 8 shows a single-phase AC remotemeasurement apparatus and method, which can be used for metering andmeasuring devices such as a single-phase electric energy meter or thelike.

In FIG. 8, an AC current i and an AC voltage u are inputted and gothrough the analog sampling channel 1 to obtain a current sampling valuei_(k) and a voltage sampling value u_(k). On one hand, the currentsampling value i_(k) and the voltage sampling value u_(k) go through amultiplication accumulator B1 to obtain active electric energy W_(k). Onthe other hand, the current sampling value i_(k) and the voltagesampling value u_(k) are filtered by a low-pass filter 61 to remove highfrequency components, re-sampled by a sampling switch 21, and theninputted to a harmonic wave decomposition device 81 to obtainfundamental and m^(th) harmonic wave vectors. The fundamental and m^(th)harmonic wave vectors, on one hand, go through an amplitude calculationcircuit 82 to obtain amplitudes of the fundamental wave and the m^(th)harmonic waves, and on the other hand, go through a power calculationdevice B2 (a conjugate of the current vector is determined, multipliedwith the voltage and then added together, and a real part and animaginary part are calculated) to obtain the active power and reactivepower of the fundamental wave and the m^(th) harmonic wave. Theamplitudes, active power and reactive power of the fundamental wave andthe m^(th) harmonic wave go through an averaging device A1 to obtaintheir average values in a steady state. The reactive power of thefundamental wave goes through an accumulator B3 to output reactiveelectric energy. The active electric energy, the reactive electricenergy, and the averages values outputted by the averaging device A1 allgo through the sampler 2 and then to register 3. The register 3, underthe control of the bus 4, outputs data through the bus 4 to thereceiving side. The fundamental wave voltage amplitude, the fundamentalwave current amplitude or the fundamental wave power goes through adetermination unit A2 to provide a flag F. When the flag F changes from1 to 0, the averaging circuit A1 is reset to zero. When F=1, the averagevalues outputted by A1 are values that cannot be reached by therespective quantities. On the receiving side, the values that cannot bereached are removed as bad data. The analog sampling channel 1 andsampling switches 2 and 21 are controlled by the timing controller 5.Other elements are as shown in the foregoing figures.

The sampling switch 21 and the low-pass filter 61 in FIG. 8 areintroduced in consideration of the insufficient computation speed ofdigital circuits. This is because that All parts, except the analogsampling channel 1, are doing digital processing, which can be performedby CPLD (Complex Programmable Logic Device), FPGA (Field ProgrammableGate Array), ASIC (Application Specific Integrated circuit) or similardigital circuits, and can also be implemented by a program of a DSP(Digital Signal Processor). The frequency of analog sampling has beendesigned to be very high in order to ensure the accuracy of activeelectric energy. However, the computation speed of digital circuits isnot high enough. Thus, re-sampling is needed and the sampling switch 21is introduced. In order to ensure that an aliasing error will not ariseafter the re-sampling, the low-pass filter 61 is introduced, and itscut-off frequency should be lower than 0.5 times the re-samplingfrequency of the sampling switch 21. If the digital processing speed ishigh enough, the low-pass filter 61 and the sampling switch 21 may beomitted.

In FIG. 8, the reactive electric energy is fundamental wave reactiveelectric energy. This is because that in a circuit involving harmonicwaves, the application first cares about the fundamental wave power, andhow much reactive power needs to be supplemented to satisfy therequirement of the power factor. It then cares about how much thecontent of harmonic waves is and which harmonic wave is bigger.Therefore, the m in the figure can be specified by the receiving side.Certainly, it is also possible to specify a plurality of harmonic wavesand obtain remote measurement results for them simultaneously. Sincethis is just a parallelization of the above circuits, it is not detailedhere.

Combining the foregoing figures, FIG. 9 shows a three-phase AC remotemeasurement apparatus and method, which can be used for metering andmeasuring devices such as a three-phase electric energy meter or thelike.

In FIG. 9, three-phrase AC currents i_(a), i_(b), i_(c) and three-phraseAC voltages u_(a), u_(b), u_(c) are inputted. In addition to theelements of FIG. 8, a positive sequence decomposition device 9 isfurther included for inputting the three single-phase fundamental wavecurrents and the three single-phase fundamental wave voltages from thefundamental wave decomposition device 81 and outputting three-phrasevoltage fundamental wave positive, negative and zero sequence vectorsand current fundamental wave positive, negative and zero sequencevectors to the amplitude calculation device 82. The amplitudecalculation device 82 outputs voltage and current fundamental wavepositive, negative and zero sequence amplitudes to the averaging deviceA1. The fundamental wave positive sequence current vector and thefundamental wave positive sequence voltage vector go through the powercalculation device B2 to obtain fundamental wave positive sequenceactive power and fundamental wave positive sequence reactive power,which are also inputted to the averaging device A1. The input to theaccumulator B3 should be the sum of the three-phrase fundamental wavereactive power. Similarly, the input to the determination unit A2 shouldbe the sum of the three-phrase fundamental wave active power. Otherelements are the same as those of FIG. 8.

If necessary, FIG. 9 may be extended to fundamental wave negativesequence or zero sequence active and reactive power, and positive,negative and zero sequence active and reactive power of the m^(th)harmonic wave.

Preferably, in addition to the elements of FIG. 9, output of positive,negative and zero sequence effect values of current and voltage isfurther provided in accordance with FIG. 4 in a remote measurementapparatus in a measurement unit for a digital substation or a powerplant. If output of waveform values is further provided in accordancewith FIG. 1, then the remote measurement requirements of varioussubstations and power plants can be satisfied.

The parts other than the analog sampling channel of the aboveembodiments can be achieved by CPLD, FPGA, ASIC or similar digitalcircuits, and can also be readily implemented by a program of a DSP.Detailed information can be found in their development manuals. It isalso possible that the analog sampling channel and the digitalprocessing parts are all integrated into one single chip.

The embodiments of the invention merely provide some specificimplementations. Various variations can be made by those of ordinaryskills in the art without departing from the spirit and concept of thepresent invention, and are all within the scope of the following claims.

What is claimed is:
 1. An apparatus for alternating current (AC)physical signal measurement and data acquisition, comprising: an analogsampling channel configured to: perform analog sampling on an input ACphysical signal to obtain an analog sampling value; a sampling switchconfigured to: re-sample the analog sampling value to satisfy arequirement by a receiving side on data acquisition frequency; aregister configured to: store a re-sampling value from the samplingswitch; a bus configured to: output the re-sampling value in theregister to the receiving side; a timing controller configured to:control the analog sampling channel and the re-sampling frequency of thesampling switch; and a digital low-pass filter, which has an inputconnected with the analog sampling value outputted by the analogsampling channel and an output connected with the sampling switch,filters out high frequency components from the analog sampling value,wherein a cut-off frequency of the digital low-pass filter is lower than0.5 times the re-sampling frequency of the sampling switch.
 2. Theapparatus for AC physical signal measurement and data acquisitionaccording to claim 1, wherein an effective value calculation device isprovided between the analog sampling channel and the digital low-passfilter, and configured to: calculate an effect value for the analogsampling value from the analog sampling channel and ouput the effectvalue to the digital low-pass filter.
 3. The apparatus for AC physicalsignal measurement and data acquisition according to claim 2, wherein afundamental/harmonic wave decomposition device is provided between theanalog sampling channel and the digital low-pass filter in parallel withthe effect value calculation device, and configured to: performfundamental/harmonic wave decomposition on the analog sampling valuefrom the analog sampling channel to obtain a fundamental/harmonic wavevector; and an amplitude calculation device, a real part calculationdevice and an imaginary part calculation device, which receive thefundamental/harmonic wave vector from the fundamental/harmonic wavedecomposition device simultaneously to output a fundamental/harmonicwave amplitude, a fundamental/harmonic wave real part and afundamental/harmonic wave imaginary part, respectively, to the digitallow-pass filter.
 4. The apparatus for AC physical signal measurement anddata acquisition according to claim 3, wherein a selection data registerconfigured to: store selection data set by the receiving side though thebus; and a selection switch is provided before the resampling valueregister, wherein for data bits controlled by the selection dataregister, when a selection bit is 1, the resampling data is selected andenters into the resampling value register; otherwise, the resamplingdata is not in the resampling value register.
 5. The apparatus for ACphysical signal measurement and data acquisition according to claim 4,further comprising: a sequence decomposition device, which performssequence decomposition on the three single-phase AC fundamental/harmonicwave vectors outputted by the fundamental/harmonic wave decompositiondevice to obtain three-phrase AC fundamental/harmonic wave positivesequence, negative sequence and zero sequence vectors, each of whichgoes through the amplitude calculation device, the real part calculationdevice and the imaginary part calculation device simultaneously tooutput three-phrase AC fundamental/harmonic wave positive, negative, andzero sequence effective values, real parts and imaginary parts, whichare filtered by the digital low-pass filter to remove high frequencycomponents.
 6. The apparatus for AC physical signal measurement and dataacquisition according to claim 3, wherein a harmonic wave frequencyregister configured to: store harmonic wave order data m set by thereceiving side to control the fundamental/harmonic wave decompositiondevice to output an m^(th) harmonic wave vector.
 7. The apparatus for ACphysical signal measurement and data acquisition according to claim 2,wherein the digital low-pass filter includes: an averaging device whichis connected with the effective value calculation device, obtains anaverage value of the effective value outputted by the effective valuecalculation device, and is then connected with the sampling switch; anda determination device which is connected with the effective valuecalculation device, and provides a flag F to the averaging device inaccordance with the effective value in the steady state or in thetransient state outputted by the effective value calculation device,wherein when the effective value is in a steady state process, F=0;otherwise, when the effective value is in a transient state process,F=1; and when F changes from 1 to 0, the average value is reset to zero,and when F=1, the average value is a value that cannot be reached,which, upon arrival at the receiving side, is removed as bad data.
 8. Anapparatus for alternating current (AC) physical signals measurement anddata acquisition, comprising: an analog sampling channel configured to:input an AC current i and an AC voltage u and output a current samplingvalue i_(k) and a voltage sampling value u_(k); a multiplicationaccumulator configured to: input the current sampling value i_(k) andthe voltage sampling value u_(k) and output active electric energyW_(k); a fundamental/harmonic wave decomposition device configured to:perform fundamental/harmonic wave decomposition on the sampling valuesto obtain fundamental and m^(th) harmonic wave vectors; an amplitudecalculation device configured to: input the fundamental and m^(th)harmonic wave vectors from the fundamental/harmonic wave decompositiondevice and output fundamental and m^(th) harmonic wave amplitudes; apower calculation device configured to: input the fundamental and m^(th)harmonic wave vectors from the fundamental/harmonic wave decompositiondevice to obtain fundamental and m^(th) harmonic wave active power andreactive power; an accumulator configured to: input the fundamental wavereactive power from the power calculation device and outputting outputreactive electric energy; an averaging device configured to: input thevoltage and current fundamental wave amplitudes from the amplitudecalculation device and the active power from the power calculationdevice and output their average values; a sampling switch configured to:input the average values from the averaging device, the active electricenergy from the multiplication accumulator, and the reactive electricenergy from the accumulator, perform re-sampling, and output theirre-sampling values; a resampling value register configured to: store there-sampling values from the sampling switch; a bus configured to: outputthe re-sampling values in the resampling value register to a receivingside; a determination unit configured to: send a flag F to the averagingdevice in accordance with the fundamental wave voltage amplitude, thefundamental wave current amplitude or the fundamental wave power in thesteady state or in the transient state, wherein when the flag F changesfrom 1 to 0, the averaging device is reset to zero, and when F=1, theoutput of the averaging device is a value that cannot be reached, whichis removed as bad data on the receiving side; a timing controllerconfigured to: perform timing control on the analog sampling channel andthe sampling switch; a selection data register configured to: storeselection data set by the receiving side through the bus to select databits to be entered into the resampling value register; and a harmonicwave frequency register configured to: store harmonic wave order data mset by the receiving side to control the fundamental/harmonic wavedecomposition device to output the fundamental and m^(th) harmonic wavevectors.
 9. The apparatus for AC measurement and data acquisitionaccording to claim 8, further comprising: a sequence decompositiondevice configured to: input the three single-phase voltage and currentfundamental wave values from the fundamental/harmonic wave decompositiondevice and output voltage and current fundamental wave positive,negative, and zero sequence vectors to the amplitude calculation device.10. A method for alternating current (AC) physical signals measurementand data acquisition, comprising: performing analog sampling on an inputAC voltage u and/or an AC current i at a sampling time interval of Δ toobtain a voltage sampling value u_(k) and/or a current sampling valuei_(k); performing low-pass filtering on the voltage sampling value u_(k)and/or the current sampling value i_(k) to remove high frequencycomponents; performing re-sampling at an interval of M_(w) designated bya receiving side (with a re-sampling frequency of f_(w)), to obtain avoltage re-sampling value u_(j) and/or a current re-sampling valuei_(j), wherein a cut-off frequency fc of the low-pass filteringsatisfies fc≦0.5×f_(w); storing the voltage re-sampling value u_(j)and/or the current re-sampling value i_(j); and outputting there-sampling values in accordance with a control signal.
 11. The methodfor AC physical signals measurement and data acquisition according toclaim 10, wherein effective values of the sampling values are calculatedbetween the analog sampling and the low-pass filtering.
 12. The methodfor AC physical signals measurement and data acquisition according toclaim 11, wherein fundamental/harmonic wave decomposition is performedbetween the analog sampling and the digital low-pass filtering inparallel with the effective value calculation to obtainfundamental/harmonic wave amplitudes, fundamental/harmonic wave realparts and fundamental/harmonic wave imaginary parts.
 13. The method forAC physical signals measurement and data acquisition according to claim12, wherein the step of outputting the re-sampling value according withthe control signal includes: setting re-sampling value register to storere-sampling value, setting selection data register to store selectiondata set by the receiving side through a bus; and providing a selectionswitch after re-sampling, wherein for selection bits controlled by aselection data register, when a selection bit is 1, the data is selectedand the re-sampling value enters into the re-sampling value register tobe stored; otherwise, the re-sampling value is not stored.
 14. Themethod for AC physical signals measurement and data acquisitionaccording to claim 12, wherein harmonic wave order m set by thereceiving side is stored to control the fundamental/harmonic wavedecomposition to output fundamental and m^(th) harmonic wave vectors.15. The method for AC physical signals remote measurement according toclaim 12, wherein sequence decomposition is performed on the threesingle-phase fundamental/harmonic wave vectors on which thefundamental/harmonic wave decomposition has been performed to obtainpositive, negative and zero sequence vectors, performing amplitudecalculation, real part calculation and imaginary part calculationsimultaneously to output fundamental/harmonic wave positive, negativeand zero sequence effective values, real parts and imaginary parts, andperforming low-pass filtering to remove high frequency components.
 16. Amethod for alternating current (AC) measurement and data acquisition,comprising: performing analog sampling on an input AC current i and anAC voltage u to output a current sampling value i_(k) and a voltagesampling value u_(k); performing multiplication accumulation on thecurrent sampling value i_(k) and the voltage sampling value u_(k) tooutput active electric energy W_(k); performing fundamental/harmonicwave decomposition on the sampling values to obtain fundamental andm^(th) harmonic wave vectors; calculating amplitudes of the fundamentaland m^(th) harmonic wave vectors to output fundamental and m^(th)harmonic wave amplitudes; calculating power of the fundamental andm^(th) harmonic wave vectors to obtain fundamental and m^(th) harmonicwave active power and reactive power; averaging the fundamental andm^(th) harmonic wave amplitudes, active power and reactive power tooutput their average values in a steady state; a determining step forsending a flag F to the average values in accordance with thefundamental wave voltage amplitude, the fundamental wave currentamplitude or the fundamental wave power in the steady state or in thetransient state, wherein when the flag F changes from 1 to 0, theaverage values are reset to zero, and when F=1, the average values arevalues that cannot be reached, which are removed as bad data on areceiving side; and accumulating the fundamental wave reactive power tooutput reactive electric energy; re-sampling the average values, theactive electric energy and the reactive electric energy to output theirre-sampling values; storing the re-sampling values; outputting thestored re-sampling values to the receiving side through a bus.
 17. Themethod for AC measurement and data acquisition according to claim 16,wherein sequence decomposition is performed on the three single-phasevoltage and current fundamental wave values from thefundamental/harmonic wave decomposition to output voltage positive,negative, and zero sequence vectors and current positive, negative, andzero sequence vectors to calculate their amplitudes.